Can I 3d Print Lego®-Style Bricks?

It occurred to me recently that I could supplement my collection of Lego® bricks with my 3d printer. My childhood was defined by Lego®. I suspect it had a big part in why I became an engineer. I had a hefty collection of Lego and I built everything from railroads to buildings to rocket ships (it was the 60s – we didn’t have starships back then!)

The yellow one is Lego®, the gray one is printed on an AnyCubic Photon

You can print Lego®-style bricks on your 3d printer. You can use a resin 3d printer (DLP or SLA) or an FDM 3d printer (using PLA, PLA+ or ABS filament). Lego’s patent in the US ran out in 1978, so it’s legal, as long as you don’t include the Lego trademark. You can design your own or download STL files from printabrick.org.

A lot of us have a pile of Lego®. Some of us have kids that have piles of the stuff. Some of us have Legos® from back when we were kids. Some even have small sets for desk ornaments or fun chachkies. And some of us are adults with a serious addiction to fun! Yes, some of us own Lego bricks and sets because they’re great to have and fun to play with. Yes, we may be attempting to capture a bygone era of childhood play, but it doesn’t take away from the shear fun of playing with construction bits to make either things already envisioned, or make things that spring from the imagination.

Sometimes, though, you may find that you have all the pieces necessary, except for a piece or two. Maybe that piece got lost when the neighbor kid stole it back 20 years ago, or the cat snuck off with it and it’s likely under the couch, or …! You’ll want a way to get a replacement part or a new part for that one model you’re trying to make. If you can’t find it for sale (and there are a lot of places to buy genuine Lego parts for sale out there – just have a look at eBay.Com and do a search – you’ll be amazed with the volume of responses!) 3d printing, of course, offers another approach that you can use. If you have an STL of the missing part, just print a copy or two or whatever’s needed, paint it and you’re off and running!

Places to Buy Replacement Lego Parts

There are likely hundreds of sellers, resellers, traders and third-party listing sites for new and used Lego bricks. Here are a few you can use, assuming you don’t want to print your own, or there’s something about the brick that makes it not possible to print. I have this problem, for example, with 4.5 Volt-style railroad wheels. They have a metal axle that makes them unsuitable for printing. Regular bricks, though, are just fine to print.

Should I Print My Bricks?

But is that legal? Can you print your own brick parts? No, you can’t produce parts with the Lego® logo on them. But in the US, the Lego patent expired back in 1978. If you leave the Lego trademark off the parts, you can print to your heart’s desire! You could even create new parts for sale, if you like. Warning! If you print a part from one of the newer Lego sets, it may still be covered by a patent, so you may be in violation. Patents tend to be valid for 20 years, so a set older than 20 years should be good to mimic. And most of the bricks in the new sets are just fine. It’s just a concern if Lego went and designed a brand-new brick that’s never been seen, and they applied for a patent on it. That’s unlikely, but theoretically possible. I’m not aware of any at the time of writing.

Finding Brick Parts in STL File Format

There is one site that’s just amazing on the web – https://printabrick.org. It has nearly every part ever created in STL format for download. You can search by part or by collection. This is especially important if you’re looking for a replacement part for a set. When I was a kid, my parents bought me a Lego railway set. That set was released in 1966 and was designated 113-2. It brought me hundreds, if not thousands of hours of fun as a kid. I did amazing things with that set, and the add-ons I received for birthdays and holidays. If I was missing a part for the train, however, it would be great to find a replacement. I remember breaking a 6 x 24 plate (part number 3026). I have both halves of the broken plate, and it’s easy to work around. However, I can now print a replacement whole part.

Printabrick.Org STL files for a Mini House

Printabrick.Org lists the set, along with every part in the set. Most of the parts are displayed as available, and the STL can be downloaded directly. I could even choose to select the entire set, have it zipped into one file, and download all of the STL files at once. There are, however, several parts that are missing from the set. I suspect that these are parts with metal in them. For example, the train wheels are unavailable. The axles are metal, and you wouldn’t be able to print those. You could approximate them but if you printed the axles, then it might be brittle and break easily. Regardless, they’re just not available from the site.

More modern sets, like MMMB006-1, a tiny little house that was available as a Monthly Mini Model Build, have all of the parts available. I haven’t done this, but it’d be just fine to download all the parts, and print the necessary number for your model, and build it. At that point, you’ve only got 3d printed parts, and no original parts.

Quality and Material

My printing has been with gray 405nm UV curing resin with an AnyCubic Photon DLP printer. I get very good quality and accuracy for the model (I print at 50 microns for the z-height). That’s better than most FDM printers can do, and I’m very happy with the results. Due to the hardness of the printed parts after curing, though, it means that getting the parts to click together, come apart and click together again can be problematic. I’ve broken a few of my printed bricks by working them too much. If your thought is to assemble the model once and leave it, then you won’t have much of an issue. I didn’t have any issues getting the parts together. It was the high amount of torque that I had to apply (and yes, that did leave circular brick dents in my hands!) that caused me to snap longer pieces. I broke another smaller pair when I couldn’t pry them apart by hand and used pliers. As they’re hollow, it’s easy to break them.

You can print the bricks with an FDM printer, using deposited filament in either PLA or ABS plastic. PLA filament is modified corn starch, so you’re safe and biodegradable. ABS is more of an oil-based plastic, and thus isn’t as environmentally friendly. Balance that, however, with the fact that actual Lego bricks are created out of ABS plastic. Filament comes in many different colors, and you could find one that’s bright and wouldn’t required painting.

Post-Printing Processing

Your printing process will likely require you to use supports to print good bricks. For FDM printers, you could print flat on the print bed and it would work just fine for flat-bottomed parts. For other parts, you’ll need supports. I use a raft and supports for every print I do with a DLP UV-curing resin printer. You’ll need to remove those supports, and file or sand the remnants of the supports from the bricks. Many bricks are either perfectly round or perfectly flat, making it easy to remove and get just right. It’s important to sand these smooth to ensure good fit. I also tend to sand the bottoms of my UV-cured resin parts, as they have a slight rounding to the surfaces, and that will bring them back to square.

Gloss spray paint is the best to mimic the glossy Lego® ABS plastic finish. Multiple light coats are better than one heavy coat.

The obvious flaw with 3d printed bricks is that they’re the color of the resin or filament unless you paint them. You can spray the bricks with gloss spray paint and it works rather well. Be careful not to spray too much on the brick and let the paint run. It will distort the size of the brick and make it difficult, if not impossible, to get the parts together. It is far better to spray a super-light coat, then let it dry, and then go back and spray again to get full coverage. Let the brick dry completely, then flip it over and spray the bottom. You can easily skip this step, but I’m a completist, and I like all sides looking bright and shiny. I have added too much paint on only one brick. I sanded down the painted surface and it fit snugly but nicely.

Designing Your Own Bricks

TinkerCad.Com is a browser-based CAD software that allows you go create, then generate STL files that you can download and use. Follow this link to use a template specifically for bricks:
https://www.tinkercad.com/things/76kjYdrSGwv-lego-bricks
It will not only save you time, but you can use it to modify and design your own bricks, with the bump spacing and brick layer heights consistent with actual bricks. Once designed, download the STL file and print just like any other STL. What will you print first? The possibilities are vast. Have a great time choosing!